Alpha CB24 no hot water to nightmare !!!

[rayuk]

To put you in the picture.....

I am a corgi gas engineer, I work with fires and cookers not boilers, so i have no prior knowledge of the workings of boilers, with that in mind i will explain my problem.
Two days ago My Moms boiler, an Alpha cb24 was only working on the heating, the water was cold or luke warm at best. It is two or three years old, don't know exactly.
The chap who installed the boiler does most of his work away from the area now and is a bu**er to get hold of, but i managed to catch him last night, after i explained what was happening he gave me a couple of things it could be, the DHW sensor or the Diaphragm.
Off i went today and purchased both parts from the local supplier, studied the service and repair manual, the countless posts on here about the same problem and then set to work.

I fitted both parts, yes it was a bit of a pain to get to some of the nuts, but all was well, or so i thought, i changed the sensor first, made no difference at all, i removed the heat exchanger, cleaned and flushed it through, it was clean as a whistle, finally i removed the diaphragm, it was rotten as a pear, i was chuffed when i saw this as i thought this was the problem.
Anyway, after putting it all back together, nothing, no hot water, no heating, fan starts, pump is running but it doesn't fire up.

What a bummer, at least before i messed with it mother had heating! needless to say i am in the dog house and i can't get in touch with the fitter, he is probably in a pub in london somewhere.

Any help at all would be appreciated before i find a fitter who might get me out of the mire.

Ray

 

[petit_pablo]

Cant picture the boiler in my head but if the pump is running and nothing else then id suggest that theres a flow switch somewhere.

Hunt this down and manually make it / bridge it out and see if this fires up the boiler

 

[fazedup71]

guessing the boiler is acting normal and only attempting to work when there is a demand for heating or hot water i would next test the air pressure switch as you say fan is running

 

[rayuk]

Cant picture the boiler in my head but if the pump is running and nothing else then id suggest that theres a flow switch somewhere.

Hunt this down and manually make it / bridge it out and see if this fires up the boiler

Yes there is a flow switch, it is clipped around the diverter, when you say bridge it out, do you mean make a conection between the terminals on the switch?

 

[gas4you]

If pump is running then flow switch has been proved I think.

What neons are flashing on the front?

 

[rayuk]

If pump is running then flow switch has been proved I think.

What neons are flashing on the front?

Bottom one only, every few seconds or so.....

 

[rayuk]

If pump is running then flow switch has been proved I think.

What neons are flashing on the front?

Bottom one only, every few seconds or so.....

 

[Eeejit]

are the neons flashing? have you refilled the system?
next thing to look at is the air pressure switch and tubes.

 

[fazedup71]

if the fan is running then there is demand for central heating or hot water, then check aps that would be the next thing to check

 

[rayuk]

are the neons flashing? have you refilled the system?
next thing to look at is the air pressure switch and tubes.

One neon is flashing every few seconds (bottom).

Refilled.....when i had finished the job i turned back on the water, the flow and return valves and opened the filling loop to get the gauge to the required setting, is this what you mean?

Air pressure switch and tubes??

 

[fazedup71]

you need to take front of combustion chamber, hell it might even fire up as you do it if it dirty in there, look for fan and some tubes connecting to a square thing, the aps might not be working, can you hear a click as fan funs up? give the air presure switch a tap, otherwise test it and clean fan, venturi etc

 

[rayuk]

you need to take front of combustion chamber, hell it might even fire up as you do it if it dirty in there, look for fan and some tubes connecting to a square thing, the aps might not be working, can you hear a click as fan funs up? give the air presure switch a tap, otherwise test it and clean fan, venturi etc

I will take a look at this tomorrow, would there be any reason why this sort of stuff would have happened even though i have'nt been messing anywhere near this??

Thanks to all for your input, much appreciated.

 

[fazedup71]

you had to drop front down to work on boiler so could you have pulled a cable? with out realising?

 

[rayuk]

you had to drop front down to work on boiler so could you have pulled a cable? with out realising?

To be honest, this did occur to me so i have checked around, can't see any loose or trailing wires, there were'nt to many about, all from the different sensors to the pcb at the front, plenty of play in the wires, under no stress while the front was down.

 

[ollski]

If the fan doesn't make high speed plug the spare sensor into the red wires to the primary sensor and see what that gives you... sounds like a problem with one of the sensors.